The present disclosure relates generally to the field of seat belt retractors for spooling seat belt (webbings) for restraining an occupant of a seat system of vehicles and the like. More specifically, this disclosure relates to a retractor having multiple independent torque transmission or absorbing systems.
A seatbelt device for use within a vehicle provides safety to an occupant by restraining the movement of the occupant during a sudden acceleration, typically resulting from a dynamic impact event of the vehicle. A typical seatbelt device includes a webbing or belt, a buckle, a tongue member to engage the buckle, a retractor, and an anchor member. Retractors include a spool and through the use of a force, often generated by a spring, wind the webbing around the spool. During a dynamic impact event of the vehicle, the retractor locks the webbing from extracting or unwinding, which restricts movement of the occupant.
It has been known to construct a retractor which includes a pretensioner and a locking mechanism. The pretensioner includes an explosive charge that rapidly generates gas during a vehicle dynamic event to create pressure to move a piston that may drive a rack, ball bearings, or any other member that may be coupled to a pinion gear through a teeth mesh. The pinion may be coupled directly or indirectly, through a member or hub, to a torsion shaft coupled to the spool, whereby rotation of the pinion transmits torque through the torsion shaft into the spool, creating torque to retract the webbing. This pretension applied to the seatbelt removes the slack between the webbing and the occupant, therefore reducing the movement that the occupant may be undergo during the dynamic impact event. The pretensioner may be deployed when sensors on the vehicle detect an impact event and are typically designed to deploy at high speed impacts. The locking mechanism may include a locking pawl driven by a force, from a spring or inertia, and having teeth to mesh with teeth of the frame member under low speed impacts, thus preventing the rotation of the spool and preventing the seatbelt from extracting. A locking pawl may be coupled to the torsion bar indirectly through other members. The torsion bar is designed to deform torsionally when subjected to a predetermined torque to absorb energy during loading, imparted by the mass of an occupant during acceleration of the vehicle, to reduce the restraint force exerted on the occupant during the dynamic impact event, thereby providing improved safety to the occupant.
When traditional retractors have a pretensioner and a spool dependently coupled, the automatic locking retractor (ALR) zone may shift due to yielding of the torsion bar from the high torque resulting from the acceleration of the occupant during a low speed dynamic impact event, when the pretensioner does not fire. This results in the ALR zone being no longer useable. This ALR zone shift may prohibit the locking mechanism from locking the retractor, allowing for extraction of the belt webbing, which reduces the ability of the seat belt system to restrain a child seat or an occupant. Additionally, the spool of these traditional retractors remains coupled to the pretensioner following deployment. This coupling creates an undesirable effect of having a delay or variable performance of energy management of the seat belt system, since to transmit torque through the torsion bar, the torque induced from restraining the occupant must overcome the energy (i.e., the torque) of the pretensioner.
Accordingly, an object of the present disclosure is to provide a cost effective retractor mechanism which includes a pretensioner and locking mechanism that are independently coupled to eliminate ALR zone shifting and additionally provide efficient energy management of the seat belt system.